1. Field of the Invention
The invention concerns a crankcase, an oil channel core for producing a crankcase, and a process for producing a crankcase according to the main claim and the dependent claims.
It is known to produce crankcases for internal combustion engines as cast parts in a sand casting or pressure casting process. Conventionally, oil channels such as oil return channels of a crankcase housing are shaped by a core withdrawal process using shaped parts or oil channel cores. For smoothing the surface of the thus produced work pieces, refractory dressings are used on the sand molds, which are applied onto the oil channel cores in order to flatten or smooth the porous surface of the oil channel cores. Conventionally, for this finely ground, thermally-stable to high-temperature fire-stable materials are employed as base material. The coating layer insulates the substrate and protects it from thermal stress due to the molten metal.
2. Description of the Related Art
In the German patent document DE 39 14 124 C2, oil channel cores are disclosed having for example a slat shape or peg-shape.
The problem therewith is that the oil return flow channels are elongate and have a narrow diameter relative to their longitudinal direction. If the oil channel core is supported, during a drying process following coating, for example during an oven treatment, on supports above and below the later produced cast part, the oil channel core bends, which can lead to a detrimental deformation of the oil return flow channel. Supporting or bearing the piece in the area between the above-mentioned support points is undesirable since the coating will become damaged at the bearing location, and during the later casting the casting material of the crankcase housing penetrates into the mold. It is a problem herein that this produces a defect that is difficult to purge.
In the utility models DE 29 812 739 U1 and DE 20 303 276 U1, specially shaped oil channel mold supports are proposed, in order to minimize the above-described problem. This type of support must however be produced separately, which necessary leads to an increase in the production costs.